W 5+ –W 5+ Pair Induced LSPR of W 18 O 49 to Sensitize ZnIn 2 S 4 for Full‐Spectrum Solar‐Light‐Driven Photocatalytic Hydrogen Evolution

The localized surface plasmon resonances (LSPR) effect makes W 18 O 49 an effective visible and near‐infrared (NIR) light antenna to realize full‐spectrum solar‐light driven photocatalysis, yet the precise origin remains elusive. Here, the LSPR originates from the localized electron confinement around lattice W 5+ –W 5+ pairs in the unique structure of W 18 O 49 by density‐functional theory calculation, which gives W 18 O 49 a broad absorption ranging from visible to NIR region, independent of the particle shape and size is confirmed. This unique periodic LSPR simplifies the design of W 18 O 49 ‐sensitized photocatalytic composite into enhancing the light absorbance of W 18 O 49 and screening photocatalytic semiconductors with suitable energy band potentials. To this end, hierarchical‐structure W 18 O 49 microflowers with high absorbance have been coated with ZnIn 2 S 4 nanosheets to achieve cocatalyst‐free photocatalytic composite, which presents an outstanding H 2 production rate of 902.57 µmol within 3 h under simulated solar‐light. Comprehensive characterizations, including ultrafast transient absorption spectroscopy, prove the injection of hot electrons from W 18 O 49 to ZnIn 2 S 4 and the increase of long‐lived active electrons. This work clarifies the LSPR origin of oxygen‐deficient semiconductors and paves the way for the search of broad‐spectrum active photocatalyst.